124 DEPARTMENT OF AGRICULTURE -GEORGIA. [410] 



After some years of cultivation, however, these ducts 

 become closed, and the water, unable to pass off through 

 them, stagnates near the surface, and injures both the soil 

 and the crops planted upon it. 



The only means of restoring such lands to fertility, will 

 be found in underdrainage. 



WHAT DRAINAGE DOES. 



1. It carries off stagnant water fiom the surface. Water 

 can only stand upon the surface of the soil when that under- 

 neath is saturated. As soon as the water is withdrawn 

 from below, that upon the surface must descend, to obey the 

 great hydrostatic law that water "seeks a level," until the 

 surface is entirely relieved. If not removed by drainage, 

 it must pass off by the slow and cooling process of evapo- 

 ration. It is stated that about "four times the amount of 

 heat is required to convert water into vapor, that is required 

 to bring it to the boiling, from the freezing point." 



Just in proportion, therefore, as the evaporation is greater 

 from underdrained than from drained soils, is there a waste 

 of heat. 



The drainage of soils which are so wet as to cause water 

 to stagnate on the surface, involves the conversion of abso- 

 lutely useless into valuable property. 



2. It removes surplus water from under tJie surface, lower- 

 ing the water level to the depth at which the drains are 

 laid. 



None of our cultivated plants except, perhaps, rice, 

 thrive on soils in which their roots find stagnant water near 

 the surface. Besides, stagnant water seems to be no less 

 noxious to our cultivated plants than to animal life, and, 

 though it may supply moisture to the soil, it seems not 

 only to be unable to supply wholesome nutrition to plants, 

 but to contain substances which are positively injurious. 

 The roots of plants grown upon undrained land, are there- 

 fore, compelled to occupy only that portion of the soil 

 which lies above the water line, which is saturated in wet 



